Early maturity, complete defoliation and boll opening are essential for the efficient machine harvesting of cotton.  Chemical topping, involving one extra application of mepiquat chloride (MC) in addition to its traditional multiple-application strategy, may be able to replace manual topping.  However, it is not known whether this chemical topping technique will influence maturity or cotton responses to harvest aids.  In this 2-yr field study, we determined the effects of the timing of chemical topping using various rates of MC on boll opening percentage (BOP) before application of harvest aids (50% thidiazuron·ethephon suspension concentrate, referred to as TE), and the defoliation percentage (DP) and BOP 14 days after TE application.  The results indicated that late chemical topping (near the physiological cutout, when the nodes above white flower is equal to 5.0) significantly decreased BOP before TE by 5.9–11.2% compared with early (at peak bloom) or middle (seven days after peak bloom) treatments in 2019, which was a relatively normal year based on crop condition.  Also, a high MC rate (270 g ha^–1) showed a significantly lower (22.0%) BOP before TE than low (90 g ha^–1) or medium (180 g ha^–1) rates.  In 2020, which was characterized by stronger vegetative growth in the late season, the late chemical topping reduced the number of leaves before TE application relative to early or middle treatments, but had lower DP (23.2–27.2%) 14 days after TE application.  The high MC rate showed a leaf count before TE application that was similar to the low and medium rates, but it showed the most leaves after TE and much lower (15.0–21.7%) DP in 2020.  These results suggest that late timing of chemical topping and a high MC rate decreased the sensitivity of leaves to harvest aids.  Further analysis indicated that the late chemical topping mainly affected the leaf drop from the mainstem and fruiting branches where the late regrowth occurred, and the high MC rate reduced leaf shedding from these parts and also from the vegetative branches.  In conclusion, chemical topping with MC during the bloom period affected cotton maturity and responses to harvest aids in different ways according to the crop condition.  To avoid the risks of delayed maturity and poor defoliation after the application of harvest aids, chemical topping should not be performed too late (i.e., near the physiological cutout) by using MC at more than 180 g ha^–1.  The optimum timing of chemical topping probably varies from peak bloom to around seven days later, and the safest MC rates for chemical topping should be less than 180 g ha^–1.

Tree peony seeds are rich in α-linolenic acid (ALA), and the peony seed oil is now being produced in China. Paeonia ostii is the most widely used tree peony species for oil extraction, which is commercially called Fengdan and treated as a single cultivar. Here, 50 P. ostii individuals from the same population in northern China were randomly selected for fatty acids (FAs) analysis. Thirteen FAs were isolated, and the most abundant five were palmitic acid (5.31–6.99%), stearic acid (1.22–2.76%), oleic acid (18.78–28.15%), linoleic acid (11.86–26.10%), and ALA (41.11–57.51%). There were significant individual differences of plants in FA quality and quantity and the linoleic acid content in Plant No. 48 even exceeded the scope of 1–99%. Further statistical analysis indicated that most of the individual FAs, saturated FAs, unsaturated FAs, and total FAs levels showed significant positive correlations to each other, whereas the seed yield per plant was independent and not correlated to the factors mentioned above. Ward’s hierarchical clustering results grouped the 50 plants into four clusters based on FA contents and seed yield, and the seven plants in Cluster IV were identified as good candidates for oil production. Our results confirmed that the individual differences did occur in P. ostii and Fengdan cannot be simply treated as one uniform cultivar. Also, these results may help simplify the selection of plants for oil peony breeding and accelerate the development of the oil peony industry.

Foxtail millet (Setaria italica (L.) P. Beauv) is a naturally stress tolerant crop.  Compared to other gramineous crops, it has relatively stronger drought and lower nutrition stress tolerance traits.  To date, the scope of functional genomics research in foxtail millet (S. italic L.) has been quite limited.  NAC (NAM, ATAF1/2 and CUC2)-like transcription factors are known to be involved in various biological processes, including abiotic stress responses.  In our previous foxtail millet (S. italic L.) RNA seq analysis, we found that the expression of a NAC-like transcription factor, SiNAC110, could be induced by drought stress; additionally, other references have reported that SiNAC110 expression could be induced by abiotic stress.  So, we here selected SiNAC110 for further characterization and functional analysis.  First, the predicted SiNAC110 protein encoded indicated SiNAC110 has a conserved NAM (no apical meristem) domain between the 11–139 amino acid positions.  Phylogenetic analysis then indicated that SiNAC110 belongs to subfamily III of the NAC gene family.  Subcellular localization analysis revealed that the SiNAC110-GFP fusion protein was localized to the nucleus in Arabidopsis protoplasts.  Gene expression profiling analysis indicated that expression of SiNAC110 was induced by dehydration, high salinity and other abiotic stresses.  Gene functional analysis using SiNAC110 overexpressed Arabidopsis plants indicated that, under drought and high salt stress conditions, the seed germination rate, root length, root surface area, fresh weight, and dry weight of the SiNAC110 overexpressed lines were significantly higher than the wild type (WT), suggesting that the SiNAC110 overexpressed lines had enhanced tolerance to drought and high salt stresses.  However, overexpression of SiNAC110 did not affect the sensitivity of SiNAC110 overexpressed lines to abscisic acid (ABA) treatment.  Expression analysis of genes involved in proline synthesis, Na⁺/K⁺ transport, drought responses, and aqueous transport proteins were higher in the SiNAC110 overexpressed lines than in the WT, whereas expression of ABA-dependent pathway genes did not change.  These results indicated that overexpression of SiNAC110 conferred tolerance to drought and high salt stresses, likely through influencing the regulation of proline biosynthesis, ion homeostasis and osmotic balance.  Therefore SiNAC110 appears to function in the ABA-independent abiotic stress response pathway in plants.

The heterotrimeric GTP-binding proteins (G-proteins) in eukaryotes consisted of α, β and γ subunits and are important in molecular signaling by interacting with G-protein-coupled receptors (GPCR), on which to transduce signaling into the cytoplast through appropriate downstream effectors. However, downstream effectors regulated by the G-proteins in plants are currently not well defined. In this study, the transcripts of AGB1, a G protein β subunit gene in Arabidopsis were found to be down-regulated by cold and heat, but up-regulated by high salt stress treatment. AGB1 mutant (agb1-2) was more sensitive to high salt stress than wild-type (WT). Compared with WT, the cotyledon greening rates, fresh weight, root length, seedling germination rates and survival rates decreased more rapidly in agb1-2 along with increasing concentrations of NaCl in normal (MS) medium. Physiological characteristic analysis showed that compared to WT, the contents of chlorophyll, relative proline accumulation and peroxidase (POD) were reduced, whereas the malonaldehyde (MDA) content and concentration ratio of Na+/K+ were increased in agb1-2 under salt stress condition. Further studies on the expression of several stress inducible genes associated with above physiological processes were investigated, and the results revealed that the expressions of genes related to proline biosynthesis, oxidative stress response, Na+ homeostasis, stress- and ABAresponses were lower in agb1-2 than in WT, suggesting that those genes are possible downstream genes of AGB1 and that their changed expression plays an important role in determining phenotypic and physiologic traits in agb1-2. Taken together, these findings indicate that AGB1 positively regulates salt tolerance in Arabidopsis through its modulation of genes transcription related to proline biosynthesis, oxidative stress, ion homeostasis, stress- and ABA-responses.